ABSTRACTHeterologous prime-boost regimens utilizing BCG as a prime vaccine probably represent the best hope for the development of novel tuberculosis (TB) vaccines. In this study, we examined the immunogenicity and protective efficacy of DNA vaccine (pcD685A) expressing the fusion protein of Ag85A and ESAT-6 (r685A) and its booster effects in BCG-immunized mice. The recombinant r685A fusion protein stimulated higher level of antigen-specific IFN-γ release in tuberculin skin test- (TST-) positive healthy household contacts of active pulmonary TB patients than that in TST-negative population. Vaccination of C57BL/6 mice with pcD685A resulted in significant protection against challenge with virulent Mycobacterium tuberculosis H37Rv when compared with the control group. Most importantly, pcD685A could act as a BCG booster and amplify Th1-type cell-mediated immunity in the lung of BCG-vaccinated mice as shown the increased expression of IFN-γ. The most significant reduction in bacterial load of both spleen and lung was obtained in mice vaccinated with BCG prime and pcD685A DNA booster when compared with BCG or pcD685A alone. Thus, our study indicates that pcD685A may be an efficient booster vaccine against TB with a strong ability to enhance prior BCG immunity.

fig4: Immunogenicity of r685A fusion protein in healthy population. A total of 17 household contacts with active TB patients were tested by TST and r685A-WBIA, respectively. Each square represents the IFN-γ concentration in a sample, and median values for TST− (n = 7) and TST+ (n = 10) groups are indicated by horizontal lines.

Mentions:
Whole blood samples were collected from 17 household contacts with active TB patients and subjected to r685A-WBIA (Figure 4). The levels of IFN-γ in all samples without antigen stimuli were below 30 pg/mL (10.6 ± 5.9 pg/mL) but significantly increased to 1401.1 ± 1084.3 pg/mL after r685A protein stimulation. Analysis of the distribution of IFN-γ levels in TST-positive and TST-negative samples showed a significant correlation between TST positivity and IFN-γ level (Figure 4). The mean IFN-γ levels in samples from TST-positive group detected by r685A-WBIA were significantly higher than those for TST-negative group (P < .05).

fig4: Immunogenicity of r685A fusion protein in healthy population. A total of 17 household contacts with active TB patients were tested by TST and r685A-WBIA, respectively. Each square represents the IFN-γ concentration in a sample, and median values for TST− (n = 7) and TST+ (n = 10) groups are indicated by horizontal lines.

Mentions:
Whole blood samples were collected from 17 household contacts with active TB patients and subjected to r685A-WBIA (Figure 4). The levels of IFN-γ in all samples without antigen stimuli were below 30 pg/mL (10.6 ± 5.9 pg/mL) but significantly increased to 1401.1 ± 1084.3 pg/mL after r685A protein stimulation. Analysis of the distribution of IFN-γ levels in TST-positive and TST-negative samples showed a significant correlation between TST positivity and IFN-γ level (Figure 4). The mean IFN-γ levels in samples from TST-positive group detected by r685A-WBIA were significantly higher than those for TST-negative group (P < .05).

Bottom Line:
The recombinant r685A fusion protein stimulated higher level of antigen-specific IFN-γ release in tuberculin skin test- (TST-) positive healthy household contacts of active pulmonary TB patients than that in TST-negative population.The most significant reduction in bacterial load of both spleen and lung was obtained in mice vaccinated with BCG prime and pcD685A DNA booster when compared with BCG or pcD685A alone.Thus, our study indicates that pcD685A may be an efficient booster vaccine against TB with a strong ability to enhance prior BCG immunity.

ABSTRACTHeterologous prime-boost regimens utilizing BCG as a prime vaccine probably represent the best hope for the development of novel tuberculosis (TB) vaccines. In this study, we examined the immunogenicity and protective efficacy of DNA vaccine (pcD685A) expressing the fusion protein of Ag85A and ESAT-6 (r685A) and its booster effects in BCG-immunized mice. The recombinant r685A fusion protein stimulated higher level of antigen-specific IFN-γ release in tuberculin skin test- (TST-) positive healthy household contacts of active pulmonary TB patients than that in TST-negative population. Vaccination of C57BL/6 mice with pcD685A resulted in significant protection against challenge with virulent Mycobacterium tuberculosis H37Rv when compared with the control group. Most importantly, pcD685A could act as a BCG booster and amplify Th1-type cell-mediated immunity in the lung of BCG-vaccinated mice as shown the increased expression of IFN-γ. The most significant reduction in bacterial load of both spleen and lung was obtained in mice vaccinated with BCG prime and pcD685A DNA booster when compared with BCG or pcD685A alone. Thus, our study indicates that pcD685A may be an efficient booster vaccine against TB with a strong ability to enhance prior BCG immunity.